1. Field of Invention
The invention relates generally to network analyzers, and more specifically to synchronizing distributed systems for monitoring and analysis.
2. Description of Related Art
Local Area Network (LAN) analysis instruments are used to measure, characterize and test data streams on LAN systems. A prior art analyzer can have a control port that allows a remote entity, typically a personal computer (PC) executing the appropriate analysis software, to control the analyzer. The connection between the PC and the analyzer is usually a physical communications link, such as an RS-232 (presently referred to as an EIA/TIA 232) serial port, or a 10/100 megabits per second Ethernet link.
Certain tests, using test systems including two or more LAN analyzers, require that a test be started and stopped on multiple system analyzers at the same time. This requirement ensures that the data gathered from multiple data streams can be correlated together. Moreover, the internal timers of the multiple analyzers need to be synchronized together to ensure that time references from multiple measurements can be correlated.
Prior art systems for synchronization of distributed network analyzers include special and distinct cabling to provide the appropriate electrical signals between analyzers in a collection of analyzers for a particular network. The prior art cabling is also designed for specific analyzer requirements. For example, the Wandel and Goltermann Technologies, Inc., (located in Research Triangle Park, N.C.) DA-30 network analyzer provides clock synchronization and counter coordination by placing two analyzers in the same cabinet with the controller computer. The controller computer""s clock is used to run both analyzers.
The network analyzers described in U.S. Pat. Nos. 5,535,193 and 5,590,116 operate most effectively when a bus, completely separate from the network to be analyzed, interconnects the analyzers. The bus for these systems preferably comprises several multiconductor computer cables that extend between parallel ports on each analyzer and the compatible port of the control computer, forming a daisy-chain parallel connection.
One disadvantage of the prior art occurs for daisy-chained, or bussed analyzers because these configurations place a limit on the number of analyzers that can be physically connected. For example, certain bus structures such as Small Computer System Interface (SCSI) buses, or IEEE 488 instrumentation buses limit the number of analyzers based on current drive and voltage limitations. For example, SCSI buses typically accommodate no more than eight analyzers. Prior art systems also typically use separate cables for control and clock information.
One aspect of the invention provides a method for synchronizing a distributed system. The distributed system includes synchronized analyzers and data streams. The distributed system supports multicast communications. The method includes selected synchronized analyzers receiving multicast information and communication packets. Each selected synchronized analyzer has processing resources including a synchronization decoder circuit, and one or more packet capture, analysis and generation circuits. The multicast information includes destination data corresponding to addresses of the selected synchronized analyzers. The synchronization decoder circuit decodes the multicast information. Responsive to the multicast information, the synchronization decoder circuit generates local signals. The synchronization decoder circuit transfers the local signals to one or more selected packet capture, analysis and generation circuits (PCAGC""s).
In some embodiments, the synchronization decoder circuit receives the multicast information. For some of these embodiments, the synchronized analyzer processing resources include a medium access controller having a first data link layer address, and a central processing unit receiving the communications packets through the medium access controller. The synchronization decoder circuit has a second data link layer address. The first data link layer address differs from the second data link layer address.
In some embodiments, the data streams comprise transmitted data packets and include monitored data streams selected for analysis at one or more monitored analysis locations. The method includes, responsive to the local signals and the communication packets, the selected PCAGC""s beginning processing of monitored data packets from monitored data streams at a start time. For some of these embodiments, the processing is adapted to analyze and manage the distributed system.
For some of the embodiments where the selected PCAGC""s begin processing, the method includes the selected PCAGC""s: capturing received monitored data packets at a monitored data receipt time, and labeling portions of the received monitored data packets with time-stamps to form time-stamped portions. The time-stamps correspond to the monitored data receipt times. The processing of the monitored data packets includes the selected PCAGC""s: analyzing the time-stamped portions, the analyzing including generating analysis data, and storing segments of the time-stamped portions and corresponding analysis data in a memory. For some of these embodiments, the distributed system includes a control unit adapted to transmit the multicast information, and the method includes the selected PCAGC""s transmitting analysis information corresponding to the analysis data to the control unit.
In some embodiments, the multicast information includes synchronization packets and control packets, and the local signals include synchronization signals and control signals. In some embodiments, the distributed system has analysis locations disposed in the data streams, and each of the selected packet capture, analysis and generation circuits is connected to one or more monitored analysis locations.
In some embodiments, the synchronization decoder circuit of a first selected synchronized analyzer receives the multicast information at a first multicast receipt time. The selected synchronized analyzers are adapted to ensure that the first multicast receipt time differs from the multicast receipt time corresponding to any other selected synchronized analyzer by no more than a maximum synchronization time. The maximum synchronization time comprises a parameter related to a smallest useful packet size and a network speed. The maximum synchronization time is less than approximately one microsecond. For some of these embodiments, the method further includes, responsive to the multicast information and the communication packets, the selected PCAGC""s completing a first process for a first set of monitored data packets, the completing for each selected synchronized analyzer occurring at an end time.
In some embodiments, the synchronized analyzer processing resources include a central processing unit. The method includes the central processing unit receiving the communication packets. Responsive to the communication packets, the central processing unit generates commands; and the central processing unit sends the commands to the PCAGC""s.
In some embodiments, the distributed system includes a control unit and a first network link. The first network link connects the control unit to the synchronized analyzers and connects the synchronized analyzers to each other. The synchronized analyzer includes a medium access controller. The method includes the control unit transmitting the multicast information through the first network link to the selected synchronized analyzers, and the control unit transmitting the communications packets through the first network link and the medium access controller to the central processing units of the selected synchronized analyzers. In other words the first network link is reused for transferring the multicast information, thereby avoiding the use of extra cabling for synchronization and control packet communication. For some of these embodiments, the control unit comprises a separate control computer. In other embodiments, the control unit comprises a master analyzer.
In some embodiments, the distributed system comprises an IEEE 802 compliant communications network.
In some embodiments, the decoding and generating local signals steps are accomplished in a decoder delay time. The variation of the decoder delay time between selected synchronized analyzers is less than approximately five percent of the decoder delay time. For some of these embodiments, the selected PCAGC""s of a first selected synchronized analyzer start processing the monitored data packets at a first start time. The first start time differs from a start time corresponding to any other selected synchronized analyzer by no more than a maximum synchronization time. The maximum synchronization time comprises a parameter related to a smallest useful packet size and a network speed, and the maximum synchronization time is less than approximately one microsecond. For some of these embodiments, the decoder synchronization circuit of a first selected synchronized analyzer transfers the local signals to the selected PCAGC""s of the first synchronized analyzer at a first transfer time (t3). The selected synchronized analyzers are adapted to ensure that the first transfer time differs from the transfer time corresponding to any other of the selected synchronized analyzers by no more than a maximum synchronization time.
A second aspect of the invention provides a synchronized analyzer for synchronizing a distributed system. The synchronized analyzer comprises a synchronization decoder circuit and one or more packet capture, analysis and generation circuits. The synchronization decoder circuit has processing resources adapted to receive and decode multicast information. Responsive to the multicast information, the synchronization decoder circuit processing resources are adapted to generate local signals. The packet capture, analysis and generation circuits processing resources are adapted to receive the local signals at signal receipt times. Responsive to local signals addressed to one or more selected packet capture, analysis and generation circuit processing resources, the processing resources thereof are adapted to capture portions of monitored data packets at monitored data receipt times. The monitored data packets are transmitted in monitored data streams. The monitored data streams are disposed in the distribution system and selected for analysis. The packet capture, analysis and generation circuits processing resources are also adapted to process the portions of the monitored data packets, the processing of the portions of the monitored data packets adapted to analyze and manage the distributed system.
In some embodiments, the synchronized analyzer includes a central processing unit having processing resources adapted to receive communication packets from a control unit disposed in the distributed system. Responsive to the communication packets, the central processing unit processing resources generate commands; and transfer the commands to the PCAGC""s. The local signals and the commands control the processing of the monitored data packets. For some of these embodiments, the distributed system includes a plurality of synchronized analyzers, a control unit having processing resources adapted to generate and transmit the multicast information, and a first network link connecting the control unit to the synchronized analyzers, and connecting the synchronized analyzers to each other. The synchronized analyzer includes a medium access controller. The central processing unit processing resources are adapted to receive communications packets from the control unit through the first network link and the medium access controller.
In some embodiments, the distributed system includes a control unit having processing resources adapted to generate and transmit the multicast information, and a first network link connecting the control unit to the synchronized analyzers, and connecting the synchronized analyzers to each other. The synchronization decoder circuit processing resources are adapted to receive the multicast information from control unit via the first network link;
In some embodiments, the distributed system comprises an IEEE 802 compliant communications network.
In some embodiments, the multicast information includes destination data corresponding to addresses of selected analyzers. The synchronized analyzer includes a medium access controller having a first data link layer address, and a central processing unit receiving data through the medium access controller. The synchronization decoder circuit has a second data link layer address, and the destination data corresponds to the second data link layer address. The first data link layer address differs from the second data link layer address.
In some embodiments, the synchronized analyzer comprises a single monitored analysis location synchronized analyzer having one or more PCAGC""s including processing resources adapted to capture monitored data packets from a single monitored analysis location. In other embodiments, the synchronized analyzer comprises a multiple monitored analysis location analyzers having a plurality of PCAGC""s. The plurality of PCAGC""s have processing resources adapted to capture monitored data packets from a plurality of monitored analysis locations.
In some embodiments, the PCAGC""s include processing resources adapted to label portions of the received monitored data packets with time-stamps to form time-stamped portions. The time-stamps correspond to the monitored data receipt times. The processing of the monitored data packets includes analyzing the time-stamped portions, the analyzing including generating analysis data, and storing segments of the time-stamped portions and corresponding analysis data in a memory. For some of these embodiments, the distributed system includes a control unit having processing resources adapted to generate and transmit the multicast information; and a first network link connecting the control unit to the synchronized analyzers, and connecting the synchronized analyzers to each other. The PCAGC processing resources are adapted to transmit analysis information corresponding to the analysis data to the control unit.
In some embodiments, the PCAGC""s have processing resources adapted to complete a first process for a first set of monitored data packets at a corresponding end time in response to the multicast information and the communication packets.
In some embodiments, the decoder synchronization circuit processing resources are adapted to decode the multicast information and generate the local signals within a decoder delay time, the variation of the decoder delay time between synchronized analyzers is less than approximately five percent of the decoder delay time.
In some embodiments, the synchronized analyzer comprises a master analyzer including processing resources adapted to transmit the multicast information to synchronized analyzers connected to the master analyzer.
A third aspect of the invention provides a system for synchronization of a distributed analysis system. The synchronization system includes data streams comprising transmitted data packets, a control unit, synchronized analyzers, and a first network link. The control unit has processing resources adapted to transmit multicast information. The synchronized analyzers are according to the second aspect of the invention. The first network link connects the control unit to the synchronized analyzers and the synchronized analyzers to each other. The control unit processing resources transmit the multicast information to the synchronized analyzers through the first network link.
In some embodiments, the distributed system has analysis locations disposed in the data streams; and each packet capture, analysis and generation circuit connected to one or more of the analysis locations. In some embodiments, the distributed system comprises an Ethernet local area network and the first network link comprises an Ethernet repeater. In some embodiments, the distributed system comprises an IEEE 802 compliant communications network. In some embodiments, the distributed system comprises a fiber distributed data interface network.
In some embodiments, the multicast information includes destination data corresponding to the addresses of selected synchronized analyzers. The synchronized analyzers include medium access controllers having first data link layer addresses, and central processing units receiving data through the medium access controller. The synchronization decoder circuits have second data link layer addresses, and the destination data corresponds to the second data link layer address. The first data link layer addresses differ from the second data link layer addresses.
In some embodiments, the packet capture, analysis and generation circuits include processing resources adapted to label portions of the received monitored data packets with time-stamps to form time-stamped portions. The time-stamps corresponding to the monitored data receipt times. The processing of the monitored data packets includes analyzing the time-stamped portions, the analyzing including generating analysis data, and storing segments of the time-stamped portions and corresponding analysis data in a memory. For some of these embodiments, the control unit includes processing resources adapted to generate the multicast information. The packet capture, analysis and generation circuit processing resources are adapted to transmit analysis information corresponding to the analysis data to the control unit.
In some embodiments, the decoder synchronization circuit processing resources are adapted to decode the multicast information and generate the local signals steps within a decoder delay time, the variation of the decoder delay time between synchronized analyzers is less than approximately five percent of the decoder delay time.
In some embodiments, the decoder synchronization circuit processing resources of a first synchronized analyzer receive the multicast information at a first multicast receipt time (t1). The synchronized analyzers are adapted to ensure that the first multicast receipt time differs from the multicast receipt time corresponding to any other synchronized analyzer in the distributed system by no more than a maximum synchronization time.
In some embodiments, one of the synchronized analyzers comprises a master analyzer including processing resources adapted to transmit the multicast information to synchronized analyzers connected to the master analyzer.
These, and other, goals and aspects of the invention will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following description, while indicating specific embodiments of the invention and numerous specific details thereof, is given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the invention without departing from the spirit thereof, and the invention includes all such modifications.